Method for Monitoring a Film Bubble, and a Film-Blowing Installation

Abstract

The invention describes a method for monitoring a film bubble ( 6 ) in an outlet region after it emerges from an outlet die and before it leaves a calibration apparatus of a blow film line, the method comprising the following steps: detecting the wavelength of the radiation emitted from at least two different locations of the outer surface of the blown film at different points in time following one another by means of at least one optical sensor determining locations of the same wavelength determining the variation over time of the locations of the same wavelength.

1 . A method for monitoring a film bubble ( 6 ) in an outlet region after exiting an outlet die ( 5 ) and before leaving a calibration apparatus of a blown film device ( 1 ), having the following steps:
 Detecting the intensities of the radiation emitted from at least two different locations on the outer surface of the blown film by means of at least one optical sensor at different, consecutive points in time   Determining locations of equal intensities;   Determining the temporal progression of the locations of equal intensities.   
     
     
         2 . The method according to  claim 1 , additionally comprising the following step: Determining at least one deviation of the locations of equal intensities from a mean value line, which runs through the mean value of the locations in the transport direction of the film in the horizontal direction, at different points in time. 
     
     
         3 . The method according to  claim 1 , additionally comprising the following step:
 Assigning the deviations to one of the following categories:
 dynamic deviations (deviations with changes over time); 
 stationary deviations (deviations without changes over time) 
   
     
     
         4 . The method according to  claim 1 , additionally comprising the following step:
 Comparing the temporal progression of locations of equal intensities for at least two different intensities.   
     
     
         5 . The method according to  claim 1 , additionally comprising the following step:
 Assigning at least one deviation to a cause of a fault.   
     
     
         6 . The method according to  claim 1 , additionally comprising the following step:
 Assigning a stationary deviation to an element of the blown film device.   
     
     
         7 . The method according to  claim 1 , additionally comprising the following step:
 Considering the influence of an element of the blown film device when determining deviations of the locations of equal intensities from the mean line.   
     
     
         8 . A blow film line for producing and monitoring a film bubble, comprising an outlet die, from the outlet region of which the film bubble can be guided out and comprising a calibration apparatus arranged downstream of the outlet die, through which the blown film can be guided, further comprising:
 a detection apparatus for detecting the intensities of the radiation emitted from at least two different locations on the outer surface of the blown film at different, successive points in time by means of at least one optical sensor and for converting the detected intensities into electrical signals;   a computing device for receiving and processing the electrical signals, wherein locations of equal intensities can be determined using the computing device, and,   wherein the temporal progression of the locations of equal intensities can be determined with the computing device.